UPWELLING (from the English words "up" (upward) and "well" (to flow) * EN: upwelling; DE: Auftriebserscheinung, Auftriebswasser; FR: upwelling; ES: corriente ascendente; RU: апвеллинг) is the uplift of the waters from the depth into the upper layers of the ocean. Upwelling is especially active within the coastal oceanic and marine zones, where the uplift of the waters proceeds under the impact of the directed winds and currents from the depth of 100-300 metres.

Powerful and stable upwelling is associated primarily with the trade-winds, and with the eastern boundary currents within the Atlantic, Pacific, and other oceans. The total area of manifestations of permanent upwelling within the modern ocean is estimated at approximately 1 million square kilometres, with average vertical speed of the uplift of the waters of 1 metre per day.

They associate with upwelling the formation of the certain types of useful minerals, for example of phosphorites. There indicates it the paleogeographic reconstruction of phosphorite-bearing basins of the pre-Cambrian and Phanerozoic, where the largest part of the largest phosphorite deposits has formed itself on the oceanic shelves, which have been washed by powerful upwellings. The circulation of oceanic waters during the process of upwelling assisted to the transfer of the large masses of cold water with phosphorus, silicon, nitrogen, and other biogenic components, which were dissolved there, in the quantities, which were measured in million tonnes, from the side of the oceanic deep waters. The active processing of geochemically mobile phosphorus (of the PO43- phosphate ion) assists to its concentration onto the productive oceanic shelves, as the result of the changes in salinity, temperature, value of pH, Eh, content of CO2, and other physical-chemical parameters of the water environment.

There plays important role for the phosphate deposition the biogenic factor, namely, various marine organisms, particularly phytoplankton, which are the consumers of dissolved phosphorus and regenerators of this element, especially within the pore waters. Upwelling assists to the formation of phosphorite at the stages of sedimentogenesis, diagenesis, and bottom rewashing of the phosphate grains, oolites, concretions, phosphatized biogenic residues, with the formation of phosphorite depositions within the valleys (depressions) of oceanic shelves during transgressions and regressions.